If the sound is dropping, something else is going on... But what? For us to figure out, we need a lot more information.. It could also be that AT is correct, and something is messy in the SFZ File...
Otherwise, its just a guess...
Seriously.. If you think it is a bug.. Type out your entire system spec. DAW? Audio card? Driver? Computer type.. OS.. Version RAM? Getting audio drop out messages? Latency settings.. Is this the only vst in the project? Etc, etc, etc...
If that sound is not sustaining, than you need to provide a lot of information, for us to begin to help you. And I'd like to try to help you..
He could be very right!
AT But if the sustain doesn't work w/ the patches it is probably due to SFZ formatting. You can try to open them in notepad and see about legnthing them.
Cheers